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Wild 'river' of storms flows to the Eastern Sierra

A series of three wet, warm storms were set to hit Mammoth and the Eastern Sierra before Monday, dumping several inches of rain on lower elevations and several feet of snow in the mountains.

Meteorologists on Thursday projected winds that could kick up to 60- to 100-miles-an-hour.

Weather watchers also had their eyes on the possibility of localized flooding.

The storms started their run at the region Wednesday morning when a subtropical, “atmospheric river” hit a big low pressure system off the West Coast, then moved inland across the Central Valley and then up along the spine of the Sierra.

Although the storms’ collective bullseye was projected to be north of Mammoth, near Sonora Pass or possibly the Lake Tahoe area, Reno National Weather Service meteorologist Bryan Brong said Mammoth was set to get wet.

“Don’t worry, you won’t get left out of this one,” he said. “There is a lot of moisture in this system. It’s one of the biggest we’ve seen this time of year in several years.”

The storms are unusual in that they are arriving with temperatures in the high 40s and low 50s—meaning much of the predicted moisture will likely fall as rain, not snow, due to the much higher snow levels associated with warm storms.

In Mammoth, Public Works Director Ray Jarvis said his crew was ready, more or less, for whatever might happen.

“Basically what we do, prior to winter really setting in, is going out and clearing out all our culverts. Frankly, we didn’t get them all done this year because of lack of manpower and the workload. We hit the ones we know generally get clogged up, so we’re OK with that.

“The other thing we normally do, especially if we’re expecting a hydrologic event when you’re going to get a let of water coming through town, and I’m not sure that’s going to happen, but on Joaquin, we have a diversion structure south of Dorrance and north of Meridian, where we can control the flow of water that comes down through that creek.

“Normally it will go diagonally through the Sierra Valley sites. We’ve closed that because that channel can’t handle a lot of water. So it’ll go into a storm drain on Dorrance and Joaquin, down behind Center Street and then down into the main storm drain, so that’s done.”

Jarvis said residents also could be proactive on their own, with help from the town and its supply of storm materials.

“The other thing we like to make available is our cinder shed. We have sand bags down there. If people feel like they need to grab some sandbags, especially for problem areas, they can do that. It’s at our yard on Commerce Drive [Industrial Park].

“Across from the main building, there’s a shed where we keep all our cinders out of the weather. There are cinders, bags, and shovels. We’d like to do this kind of work ourselves, but we don’t have time to do it.”

Flooding is the biggest threat below 8,000 feet. A more typical pattern for Mammoth in late November/early December is colder storms, where the snow level is lower.

The second storm was forecast to come in Thursday evening and last into Friday (Nov. 30), Brong said, accompanied by high winds and a mix of blowing snow and rain.

The third, likely to be the biggest snow producer for the Mammoth area, is forecast to arrive Saturday evening and last into much of Sunday. Although that storm is the biggest of the three and the coldest, it is also coming at the tail end of the five-day system, making it hard to pinpoint how much snow the area will get, Brong said. Predictions for snow on top of Mammoth Mountain ranged between two to five feet by the end of the five-day system, depending on where the storm comes in and exits.

Three main variables could cause some trouble for communities and travelers, Brong said.

First, the storms were slow moving, meaning they were set up over a region, taking their time before moving out.

The second, the storms were uncharacteristically warm for this time of year, meaning much of the moisture is projected to fall as rain, not snow, except at the higher elevations.

Third, the storms were coming in with very high winds, as much as 100 miles an hour at the top of Mammoth Mountain and as much as 75 miles an hour in canyons and other areas that tend to funnel wind, such as Walker Canyon.

“For anyone travelling U.S. 395, the wind could be a big problem,” said Brong.

Downed trees and tree limbs were another possible effect from the wind, and with it, possible power outages.

“All of my people are on call throughout this week and I have a few from another department that are licensed to drive our big vehicles also on call,” said Jeff Walters, the county’s roads and maintenance supervisor.

Sandbags are ready to go should they be needed, he said.

Landslides are another possible problem in the county, where roads run under steep, boulder-strewn slopes. Areas like the Twin Lakes area west of Bridgeport and Lower Rock Creek Road and parts of Crowley Lake Drive (the portion between Crowley Lake and Aspen Springs) are prone to rock falls and/or landslides.

Walters said his crews would be making runs through those areas every day, removing rocks and debris.